Our objectives are to identify morphologic characteristics which consistently are associated with cleft lip and/or palate probands and to test such features for occurrence in immediate family members. We will use an extensive set of data on families having a set of twins at least one of whom has a cleft lip and/or palate. We plan to (1) study probands in the data set to find characteristics consistently associated with oral clefts, (2) study co-twins, sibs, and parents for the associated characteristics to help define "carrier" status, (3) look for patterns of occurrence of the associated characteristics in the cleft palate twin families to suggest and test possible models of inheritance, and (4) to validate our results from the twin data set by utilizing data from the Cleft Palate Clinic. We are in a good position to carry out this research for four reasons: (1) the existence of a theoretical model on which to base our studies; (2) our access to a data set uniquely applicable to the problem, (3) our experience and ability to formulate and complete the analysis required and (4) the promise of completed pilot studies.